1. Field of the Invention
This invention related to novel processes for the production of unnatural penicillins anc cephalosporin derivatives thereof.
2. The Prior Art
It has been reported (Journal of Antibiotics 29, 1258 (1976) RIT2214, "A New Biosynthetic Pencillin Produced by a Mutant of Cephalosporium Acremonium") that a mutant of C. acremonium produces a compound having the formula ##STR2## when the medium is supplemented with L-S-Carboxymethyl cysteine ##STR3## Compound (1) is a Penicillin N analog by virtue of its D-S-carboxymethyl cysteine side chain and is more active in vivo than ampicillin. It may also be synthesized from the reaction of a penicillin ##STR4## with D cysteine. Penicillin (3) may be prepared, on an industrial scale, by reaction of 6-aminopenicillanic acid (6-APA): ##STR5## with bromoacetyl chloride ##STR6## These processes are not, however, believed to be commercially viable as the mutant which produces compound (1) is not sufficiently stable for industrial use; the process which produces compound (1) following addition of (2) to the medium may also produce other penicillins and cephalosporins which are difficult to separate; and further the chemical synthesis requires the use of relatively expensive (Ca $50/gram) D-cysteine as opposed to L-cysteine (Ca $50/kilogram). It is also known (Biochemical Journal 179, No. 1, April 1979 "Biosynthesis of a 7-methoxycephalosporin" that a cell free preparation of S. clavuligerus converts the cephalosporin compound: ##STR7## into the cephamycin: ##STR8## It is also known (Journal of Antibiotics 36, 229, (1983) "Synthesis and Biological Activity of 7.beta.-(2-Amino-2-carboxy)-Ethylthioacetamido-7-.alpha.-Methoxycephalospo rin Derivatives") that cephalosporins ##STR9## where R=H, OCH.sub.3, having a D-S-carboxymethyl-cysteine side chain, have a high order of antibacterial activity in vivo. Such cephalosporins are, however, difficult to synthesize and require a multistep process beginning with a natural product, in addition to requiring a process for D-carboxymethylcysteine.
In our earlier filed application for Letters Patent of the United States, Ser. No. 410,302, now U.S. Pat. No. 4,510,246, and Ser. No. 507,852, now U.S. Pat. No. 4,536,476, there is described a biological process using three enzymes (cyclase, epimerase, and ring expansion enzymes) derived from S. clavuligerus or other prokaryotic organisms such as S. cattleya and S. lipmanii, which sequentially cyclizes ACV (L-Aminoadipyl-L-cysteinyl-D-valine) ##STR10## to isopenicillin-N: ##STR11## which is then epimerized to penicillin N ##STR12## and finally ring expanded to desacetoxycephalosporin C ##STR13## The prokaryotic .beta.-lactam producing organisms S. clavuligerus, S. cattleya and S. lipmanii referred to above are publically available from either the American Type Culture Collection, Rockville, Md., or Northern Regional Research Laboratory, Peoria, Ill., under the following accession numbers:
______________________________________ ATTC NRRL ______________________________________ S. clavuligerus 27064 3585 S. cattleya 39203 8057 S. lipmanii 27357 8584 ______________________________________